Coupling between Pyroelectricity and Built-In Electric Field Enabled Highly Sensitive Infrared Phototransistor Based on InSe/WSe₂/P(VDF-TrFE) Heterostructure

The assorted utilization of infrared detectors induces the demand for more comprehensive and high-performance electronic devices that work at room temperature. The intricacy of the fabrication process with bulk material limits the exploration in this field. However, two-dimensional (2D) materials with a narrow band gap opening aid in infrared (IR) detection relatively, but the photodetection range is narrowed due to the inherent band gap. In this study, we report an unprecedented attempt at the coordinated use of both 2D heterostructure (InSe/WSe2) and the dielectric polymer (poly(vinylidene fluoride-trifluoroethylene), P(VDF-TrFE)) for both visible and IR photodetection in a single device. The remnant polarization due to the ferroelectric effect of the polymer dielectric enhances the photocarrier separation in the visible range, resulting in high photoresponsivity. On the other hand, the pyroelectric effect of the polymer dielectric causes a change in the device current due to the increased temperature induced by the localized heating effect of the IR irradiation, which results in the change of ferroelectric polarization and induces the redistribution of charge carriers. In turn, it changes the built-in electric field, the depletion width, and the band alignment across the p-n heterojunction interface. Consequently, the charge carrier separation and the photosensitivity are therefore enhanced. Through the coupling between pyroelectricity and built-in electric field across the heterojunction, the specific detectivity for the photon energy below the band gap of the constituent 2D materials can reach up to 1011 Jones, which is better than all reported pyroelectric IR detectors. The proposed approach combining the ferroelectric and pyroelectric effects of the dielectric as well as exceptional properties of the 2D heterostructures can spark the design of advanced and not-yet realized optoelectronic devices.